Context: Because of its ongoing access to the majority of the U.S. population, the primary care setting has great potential for preventing and managing cardiorespiratory illness. However, due to their broad focus and competing demands, primary care practices often fail to translate evidence-based guidelines into practice. Background: Based on more than 10 years of practice-based observational and intervention research, we developed a multimethod assessment process (MAP) for understanding the unique barriers, opportunities and complexity of diverse primary care practice settings. MAP has been used to inform a practice-individualized intervention that resulted in sustained increases of evidence-based guidelines for clinical preventive service delivery. We integrated a participatory quality improvement (PQI) process that involves patients, office staff, and physicians with MAP (MAP/PQI) to enhance and promote ongoing practice-specific quality improvement. Purpose: This study will evaluate whether the innovative MAP/PQI intervention increases adherence to multiple cardiorespiratory guidelines in primary care practice. Methods: A group randomized clinical trial of 60 primary care practices representing diverse patient populations and payment systems will be conducted. After a 2-year follow-up, the control group will cross-over to a refined delayed intervention. MAP at each practice will identify features that foster and/or impede adherence to screening and treatment guidelines for multiple cardiorespiratory diseases among the competing demands of practices. PQI will then engage clinicians, staff, and patients in implementing tailored improvements that target the whole practice and simultaneously focus on changes that affect multiple guidelines. Rates of adherence to multiple guidelines will be compared for intervention and control practices. A comparative case study process analysis will identify features associated with success. These insights will be incorporated into a refined intervention for the control group (delayed intervention), and evaluated in a pre/post design. Significance: Tailoring MAP/PQI to unique practice characteristics is likely to result in sustained increases in adherence to cardiorespiratory guidelines. The intervention will be translatable into ongoing implementations of evidence-based guidelines in the primary care setting where the majority of Americans receive their medical care.